Certain microorganisms exist that can kill plant pathogens or reduce their populations. These are called antagonists.
A well-known antagonistic fungus is Trichoderma sp., which is commercially available in several countries including Thailand.
Trichoderma can be used to suppress soil-borne pathogens that cause diseases such as damping-off, root rots, stem rots, and wilting in many vegetables. It is usually used by mixing it into the soil a few days before planting, but it can also be used in making compost.
While it can also be used to cure crop diseases, it is generally more effective when applied as a preventive measure.
Besides its effect as a natural enemy of plant pathogens, Trichoderma has also a good effect on plant growth as it improves soil fertility by acting as a decomposer.
Trichoderma can also be used to treat seeds as a protection against seed-borne fungal diseases.